1. Field of the Invention
The present invention relates to a claw apparatus for a liquid electrophotographic printer and, more particularly, to a claw apparatus for a liquid electrophotographic printer which can prevent a paper jam phenomenon from occurring as a sheet of paper passing between a transfer roller and a fixation roller adheres on and is rolled on the surface of the transfer roller by a peel force.
2. Description of the Related Art
In a typical liquid electrophotographic printer, an electrostatic latent image formed on a photoreceptor medium, such as a photoreceptor web, is developed with developer having a predetermined color, and a toner image formed on the photoreceptor medium is transferred to a sheet of paper to print a desired image.
As shown in FIG. 1, the typical liquid electrophotographic printer includes a photoreceptor medium 1 circulating in a direction indicated by arrow A, and a development unit 2 disposed under the photoreceptor medium 1. An electrostatic latent image is formed by a laser scanning unit LSU (not shown) on the surface of the photoreceptor medium 1. The electrostatic latent image is developed by toner of the developer injected by the development unit 2 and a toner image is formed. The toner image is transferred to a sheet of paper 7 by a transfer unit 10. The transfer unit 10 includes a transfer roller 3 for receiving the toner image formed on the photoreceptor medium 1 due to the difference in surface energy between the photoreceptor medium 1 and the transfer roller 3, and a fixation roller 4 for pressing the transfer roller 3 to transfer the image on the transfer roller 3 to the paper 7 utilizing the difference in surface energy between the transfer roller 3 and the paper 7. Reference numeral 5 denotes a backup roller for supporting the photoreceptor medium 1 and guiding circulation of the photoreceptor medium 1.
As it is well-known, not only the surface of the photoreceptor medium 1 can be charged by a charger (not shown), but also the level of electric potential of the surface of the photoreceptor medium 1 can be selectively converted by beam scanning of the laser scanning unit. In a typical liquid electrophotographic printer, the entire surface of the photoreceptor medium 1 is charged by a corona charge to an electric potential of about 600 volts and the electric potential of the surface of the photoreceptor medium 1 is selectively dropped to about 150 volts by the laser scanning unit, so that a predetermined electrostatic latent image is formed. When toner charged to the electric potential of about 450 volts is added to the above electrostatic latent image, the toner adheres to only a portion where the level of electric potential is dropped and accordingly an image is formed.
A conventional claw apparatus 6 is installed adjacent to the transfer roller 3 to prevent a jam occurring as the paper 7 passing between the transfer roller 3 and the fixation roller 4 proceeds while adhering to the surface of the transfer roller 3 due to a peel force. This is because the jam phenomenon can be prevented when the leading end of the claw apparatus 6 is disposed at least at a point where the leading end of the paper 7 is separated about 0.5 mm from a contact point between the transfer roller 3 and the fixation roller 4. However, as the leading end of the claw apparatus 6 has a mechanical allowance of .+-.0.2 mm, the jam phenomenon is difficult to eliminate unless the claw apparatus 6 is precisely processed. Also, to provide an additional unit to prevent the jam phenomenon makes the structure of the printer more complicated.